Thermal cut-out



1929- G. w. O'KEEFFE Q 1,737,673

THERMAL CUT-OUT F1104 Duo. 11, 1924 Patented Dec. 3, 1929 UNITED STATES- PATENT OFFICE GEORGE W. OKEEFFE, OF DORCHESTER, MASSACHUSETTS, ASSIGNOR, BY MESNE AS- SIGNMENTS, TO CONDIT ELECTRICAL MANUFACTURING CORPORATION, OF BOSTON, MASSACHUSETTS, A CORPORATION OF MASSACHUSETTS THERMAL CUT-OUT Application filed December 11, 1924. Serial No. 755,347.

This invention relates to electric cut-outs especially adapted for electric motor protection and of the type having two relatively-separable circuit-interrupting members biased for separating movement and normally held in current-conducting relation by a member which is adapted to fuse readily upon overload, whereby to release said circuit-interrupting members for operation to interrupt the circuit.

The object of this invention is to provide a simple, cheap and reliable cut-out of the type above set forth.

Fig. 1 is an elevation of an electric cut-out embodying the invention.

Fig. 2 is a plan view of Fig. 1.

Fig. 3 is a plan sectional view taken line 3-3 of Fig. 1.

I Fig. 4 is an enlarged sectional elevation taken along line44 of Fig. 8.

Fig. 5 is a perspective view of the circuitinterrupting mechanism.

Fig. 6 is a perspective view of the fusible element.

Fig. 7 is a plan view of the cut-out, with the cover removed, and illustrating the relative position of the parts after circuit-interruption.

' Fig. 8 is a view similar to Fig. 7 but with the mechanism removed.

The electric cut-out embodying the invention includes an insulating enclosing casing composed preferably of porcelain. Said casing is formed with an enlarged upper circular portion 10 and a reduced lower circular portion 12 about which an externally screwthreaded metal shell 14 is secured, whereby the device may be received removably in a supporting socket. The lower portion of the casing is formed or provided with an internal axial recess, or wall, 16 and the upper portion of the casing is formed or provided with an along internal recess, or compartment, 18 in communication with said well 16. Said compartment is adapted to be closed at the top by the removable cover 20.

The circuit is adapted to be interrupted in said compartment 18 by means including the fusible link illustrated in Fig. 6. Said link includes two circuit-interrupting members 22 is formed with the hook 28.

and 24 formed of wire and having their proximate ends abutted and secured in such relation by a mass 26 of readily fusible metal, as a low melting point solder. Said members 22 and 24 are adapted to be traversed by an electric current and become heated; and for this purpose may be composed of some suitably high resistance material. The heat in said members is adapted to be conducted into the mass of fusible metal, and ultimately heat it, whereby to release said two members; and means, hereinafter to be described, are provided to separate said members rapidly, whereby to interrupt the circuit.

Said fusible link is adapted to be connected loosely and removably with the terminals of the cut-out and, to this end, said member 22, The member 24 is bent at approximately right angles, intermediate its length, and the free end thereof is formed with a hook 230, which hook is offset downwardly from the general plane of the member.

One of the cut-out terminals comprises a conducting member 32 which has its upper end disposed in a recess 84 in the upper com partment and is extended downwardly and is connected to the shell 14 by solder or otherwise. The upper end of said member 32 has a refiexed portion 36, as illustrated in Fig. 4, and is provided with a clamping screw 38 beneath which the hook 80 of the fusible link is adapted to be received. 7

The other terminal of the cut-out includes an arm 40 which has an upwardly-extended projection 42 over which the hook 28 of the fusible link is adapted to be disposed. The end of said arm opposite said projection is fixed in a slot 44 formed in the end of a vertical shaft 46. Said shaft is disposed to rotate in the recess 16 of the enclosing casing and the lower end thereof is formed with a reduced and externally screw-threaded extension 48. Said shaft extension is rotatably received within the internally screw-threaded axial recess 50 of a bushing 52. Said bushing is disposed in the bottom of the enclosing casing and extends axially therethrough to form the exposed center terminal of the cut-out. Said bushing may have the enlarged head 54 which cooperates with the nut 56 to secure the bushing in place.

An insulating sleeve 58 is disposed over said shaft 46, above the screw-threaded lower end, and the upper end of said sleeve is slotted to receive said arm 40, which arm serves to lock said sleeve to the shaft against rotation thereon. Said sleeve serves to protect the said shaft against contact with the circuitinterrupting arc. A helical spring 60 loosely surrounds said sleeve, at the lower end thereof and the upper end 62 of said spring is anchored in said sleeve. The lower end 64 of said spring is disposed in a vertical slot 6.6 of the casing and is thereby anchored to the casing. Said spring is arranged to bias said shaft 46. and arm 40 for counter-clockwise rotation, Fig. 7, and thereby constantly exert a tension on the fusible link tending to separate the members 22 and 24 thereof. A 5 ring washer 68 is disposed between said busliing 52 and the shoulder of said shaft 46 whereby to main ain a firm hearing between said, shaft 46 andbushing. Said shaft 46, and bushing, 52 may be withdrawn from the casing as a unit upon the removal of nut 56.

The normal, or operative, position of the parts is illustrated in. Fi 3. When the current traversing the fusi le link is sufficient to soften or melt, the mass. of fusible metal 26, said spring. 60. acts to snap, the loosened circuit-interrupting member 22 of the fusible link away from its cooperating member whereby to interrupt the circuit rapidly; and an abutment 70 of the casing serves to limit such movement of the arm 40;

The slot 44 in the upper end of the shaft 46 is adapted to receive the head of a screwdriver or similar instrument, whereby said shaft and its arm may be rotated against the action of said s ring 60, for the purpose of inserting a new sib e link.

The structure may be otherwise modified without departing from the spirit of the in vention.

I claim:

1. A current limiting electric cut-out comprising a casing having a air of exposed terminal members adapted or detachable connection with a cut-out block, a fixed, terminal connected with one of said terminal members, a movable terminal connected with said other terminal member and including a rotatablysupported shaft having a laterally-extended arm, a. current limiting fusible link connectin said arm and fixed terminal, and means to s said movable terminal for movement away from said fixed terminal.

2An electric cut-out including an enclosin casing provided with an external screwthreaded terminal shell, a fixed terminal disposed within said casing and connected with said terminal shell, a movable terminal including a rot-atably-supported shaft having a laterally-extending arm, a fusible link connecting said arm and fixed terminal, and a spring encircling said shaft arranged constantly to urge said arm away from said fixed terminal.

3. A plug type electric cut-out including an enclosin casing having an externally screw-three ed terminal shelzl, a fixed terminal disposed within said casing and electrically connected: with said shell, a movable terminal including a rotatably-supported shaft having a laterally-extended arm which is disposed within said casing, and means to bias said shaft for rotary movement in a direction to move said arm away from said fixed terminal.

4. An electric cut-out including an enclosing casing having an externally screw-threaded terminal shell, a fixed terminal disposed within said casing and electrically connected with said shell, a movable terminal disposed within said casing and including a rotatably-supported shaft having a laterallyextended arm, and means to bias said shaft for rotary movement in a direction to move said arm away from said fixed terminal, and a fusible link connecting said fixed terminal and arm and arran ed normally to restrain said shaft from suci movement;

5. An electric cut-out comprising an enclosing casing rovided with a screw-threaded terminal she I, a rotatably-supported shaft disposed within said casing approximately in the axis of said shell, said shaft having a laterally extended arm, and means urgin said shaft to revolve said arm transversely 0% said shell-axis.

6. An electric cut-out comprising an enclosing casing rovided with a screw-threaded terminal she l, a, rotatably-supported shaft disposed within said casing approximately in the axis of said shell, said shaft having a laterally-extended arm, means urging said shaft to revolve said arm transversely of said shell-axis, a fixed terminal connected with said shell, and means including a fusible link connecting said fixed terminal and arm.

7. An electric cut-out comprising an enclosing casin provided with a screw-threaded terminals ell, a rotatably-supported shaft disposed within said casing approximately in the axis of said shell, said shaft having a laterally extended arm, and means including a s rin r encircling said shaft and connected wit. said shaft and casing arranged to urge said shaft to revolve said a'rm transversely of said shell-axis.

8'. A plugtype electric cut-out comprising a fixed terminal and a movable terminal co operating therewith, said movable terminal including a shaft having a laterally-extended arm at the upper end and a screw-threaded extension at the lower end, a supporting member into which said extension is loosely screw-threaded and is freely rotatable in the screw threads, and a spring encircling said shaft arranged to bias said shaft to revolve said arm away from said fixed terminal.

9. A plug type electric cut-out comprising a fixed terminal and a movable terminal cooperating therewith, said movable terminal including a shaft having a laterally-extended arm at the upper end and a screw-threaded extension at the lower end, a supporting member into which said extension is loosely screw-threaded and is freely rotatable in the screw-threads, a spring-bearing washer interposed between said shaft and supporting member, and a spring encircling said shaft arranged to bias said shaft to revolve said arm away from said fixed terminal.

10. A plug type electric cut-out comprising a fixed terminal and a movable terminal cooperating therewith, said movable terminal including a shaft having a laterally-extended arm at the upper end and a screw-threaded extension at the lower end, a supporting member into which said extension is loosely screw-threaded and is freely rotatable in the screw threads, a spring encircling said shaft to revolve said arm away from said fixed terminal, and an insulating bushing disposed over the upper end of said shaft.

11. An electric cut-out comprising an enclosing casing having a screw-threaded terminal-shell at its lower end, an internally screwthreaded terminal-bushing extended through the lower end of said casing along the axis of said shell, a shaft disposed within said casing approximately in the axis of said shell and having a lower externally screw-threaded extension rotatably received within said bushing, a spiral spring encircling said shaft to bias said shaft for rotary movement, an arm extended laterally from the upper end of said shaft and having an upstanding extension adapted removably to receive one end of a fusible link, and a terminal disposed within said casing and connected with said terminal-shell arranged to receive the other end of a fusible link.

12. An electric cut-out comprising a fixed terminal and a cooperating movable terminal, said movable terminal including a shaft having a laterally-extended arm at its upper end and a screw-threaded extension at its lower end, a supporting member into which said extension is loosely screw-threaded, an insulating tube disposed over said shaft and having a slot at its upper end in which said arm is received, whereby to lock said Shaft and tube against independent rotation, and a helical spring encircling said bushing and having one end attached to said bushing and having its other end anchored, whereby to rotate said shaft.

13. A fusible member for an electric cutout comprising two relatively stifi conducting members of relatively high resistance material in which heat is adapted to be 'developed having abutted proximate ends, and hooked free terminal ends, and a readily fusible metal connecting said abutted ends, said hooked ends being disposed in different planes.

14. A fusible member for an electric cutout comprising two relatively stiff conducting members in which heat is adapted to be developed having abutted proximate ends, and hooked freeterminal ends, and a readily fusible metal connecting said abutted ends, said hooked ends being disposed in different planes, and one of said conducting members refiexed approximately at right angles intermediate its ends.

15. An electric cut-out comprising a casing having insulating walls shaped and arranged to provide a curved arc passage, a fixed terminal located in said passage at one end thereof, an arm comprising a second terminal having a pivotal support external of said passage and having a section disposed therein and capable of movement therealong, a spring biasing said arm for movement away from said fixed terminal, and a fusible link disposed within said passage and connected with said fixed terminal and arm-section and adapted normally to hold said arm from movement and to rupture upon excessive current passing through it.

16. An electric cut-out comprising a casing having an open top, a fixed terminal located within the casing at one side thereof, an upstanding shaft having a rotatable support within said casing and comprising a second terminal, a laterally-extended arm, a spring biasing said shaft for rotation of its arm away from said fixed terminal, said arm and fixed terminal having provision for supporting and being electrically connected by a connecting link rupturable under excessive current passing through it, and said shaft having a transverse screw-driver slot in its upper end by which a screw-driver can engage and rotate said shaft against its spring.

In testimony whereof, I have signed my name to this specification.

GEORGE W. OKEEFFE. 

